1. Field of the Invention
This invention is related to a method for improved electrical contact quality and current distribution in an electrically-pumped (Al,In,Ga)N Vertical-Cavity Surface-Emitting Laser (VCSEL), and a structural design for an electrically-pumped (Al,In,Ga)N VCSEL utilizing these improvements.
2. Description of the Related Art
(Note: This application references a number of different publications as indicated throughout the specification by one or more reference numbers within brackets, e.g., [x]. A list of these different publications ordered according to these reference numbers can be found below in the section entitled “References.” Each of these publications is incorporated by reference herein.)
There is a need for optical sources for various commercial, industrial, or scientific applications. Due to several inherent advantages of VCSEL devices, such as their ability to form densely packed arrays, on-wafer testing, and low power consumption, these devices may offer a lower cost alternative to traditional edge-emitting lasers and improved performance over Light Emitting Diodes (LEDs).
VCSELs may find utility in applications such as full-color displays, where the VCSEL's small spot size and higher power will yield higher brightness and higher resolution images and lighting displays (compared to those using LEDs). These structures are ideal for solid-state lighting and may offer much higher wall-plug efficiencies than can be achieved with LEDs. Another application, which results from the shorter wavelength and smaller spot size provided by (Ga,In,Al)N VCSELs, is high resolution printing and high throughput printing. Additionally, large arrays could increase printer throughput. (Ga,In,Al)N VCSELs could also provide a simple and low-cost optical head for next generation optical data storage.
At this time, (Ga,In,Al)N VCSELs only exist as optically pumped structures [1-3]. These structures require the implementation of large and costly pumping lasers, which limits their practical and commercial utility. Electrically pumped structures have been proposed and preliminary results have been reported [4,5]. However, they have not been successful and have required either difficult fabrication techniques or difficult epitaxial growths. In addition, they lack the benefits of an integrated micromirror or intra-cavity metal contact and current distribution layer.
There is a need, then, for improved methods of generating electrically-pumped VCSELs. The present invention satisfies that need.